Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751547AbaKQJuk (ORCPT ); Mon, 17 Nov 2014 04:50:40 -0500 Received: from service87.mimecast.com ([91.220.42.44]:60624 "EHLO service87.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751653AbaKQJuj convert rfc822-to-8bit (ORCPT ); Mon, 17 Nov 2014 04:50:39 -0500 Message-ID: <5469C503.9010007@arm.com> Date: Mon, 17 Nov 2014 09:50:59 +0000 From: Juri Lelli User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.2.0 MIME-Version: 1.0 To: Wanpeng Li , Wanpeng Li , Ingo Molnar , Peter Zijlstra CC: Kirill Tkhai , "linux-kernel@vger.kernel.org" , "juri.lelli@gmail.com" Subject: Re: [PATCH 2/2] sched/deadline: fix start high-res preemption tick for a non-running task References: <1415670747-58726-1-git-send-email-wanpeng.li@linux.intel.com> <1415670747-58726-2-git-send-email-wanpeng.li@linux.intel.com> <54647BDC.6050804@arm.com> <5464882D.40504@gmail.com> In-Reply-To: <5464882D.40504@gmail.com> X-OriginalArrivalTime: 17 Nov 2014 09:50:36.0684 (UTC) FILETIME=[F00B9CC0:01D0024B] X-MC-Unique: 114111709503606901 Content-Type: text/plain; charset=WINDOWS-1252 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On 13/11/14 10:30, Wanpeng Li wrote: > Hi Juri, > On 11/13/14, 5:37 PM, Juri Lelli wrote: >> Hi, >> >> not sure I understand what the problem is here. >> >> On 11/11/14 01:52, Wanpeng Li wrote: >>> Queued ticks are scheduled to match the budget, which means the budget >>> is overall consumed and the dl task should be throttled. >> ... enforce the budget? It means that when the budget is consumed the >> task has to be throttled... > > Agreed. > >> >>> Dl task will >>> be replenished immediately if fail to start a dl timer. >>> >>> However, the curr maybe not the left most dl task in the rb tree any >>> more after this immediately replenished and reschedule is needed. >>> Start high-res preemption tick for this upcoming rescheduled dl task >>> is not correct. >>> >> So, the task that is going to preempt curr is picked by >> pick_next_task_dl(), that correctly starts the hrtick for this new task. >> >> Maybe you can add more information about what you are seeing? A callpath >> maybe? > > The parameter of task_tick_dl() queued == 1 means that hrtick is fired. > hrtick() => task_tick_dl( , ,1), so p->dl.runtime should be <= 0 if > queued == 1. What I see is queued == 1 && p->dl.runtime > 0 && p is not > the left most task and hrtick is start for this task. > Oh, right, now it makes sense. Good catch! :) Could you please post a second version with a more explanatory changelog and maybe a comment just above the check? Thanks, - Juri > Regards, > Wanpeng Li > >> >> Thanks, >> >> - Juri >> >>> This patch fix it by not starting high-res preemption tick for a >>> non-running dl task. >>> >>> Signed-off-by: Wanpeng Li >>> --- >>> kernel/sched/deadline.c | 3 ++- >>> 1 file changed, 2 insertions(+), 1 deletion(-) >>> >>> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c >>> index 56674f6..2a6a5bb 100644 >>> --- a/kernel/sched/deadline.c >>> +++ b/kernel/sched/deadline.c >>> @@ -1090,7 +1090,8 @@ static void task_tick_dl(struct rq *rq, struct task_struct *p, int queued) >>> { >>> update_curr_dl(rq); >>> >>> - if (hrtick_enabled(rq) && queued && p->dl.runtime > 0) >>> + if (hrtick_enabled(rq) && queued && p->dl.runtime > 0 && >>> + is_leftmost(p, &rq->dl)) >>> start_hrtick_dl(rq, p); >>> } >>> >>> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html >> Please read the FAQ at http://www.tux.org/lkml/ > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/